Aromatic polycarbonate resins (hereinafter abbreviated as “PC resin”) exhibit excellent heat resistance, mechanical properties, electrical properties and dimensional stability and the like, and are therefore widely used in all manner of fields, including within automobile members, OA (office automation) equipment, information and telecommunication equipment, electrical and electronic instruments, and household electrical appliances and the like. However, because these PC resins are usually amorphous, the molding temperature tends to be high, meaning the resins suffer from poor melt fluidity.
In recent years, molded products within the applications listed above have become increasingly larger, thinner and more complex in shape, and as a result, there are considerable demands for improvements in the melt fluidity of PC resins during molding.
Patent Document 1 proposes, as a method of improving the melt fluidity of a PC resin during molding without impairing the excellent properties (such as the heat resistance and mechanical properties) of the resin, a method in which a copolymer of styrene and phenyl methacrylate is used as a fluidity improver and added to the PC resin. However, although this method improves the melt fluidity of the PC resin, the heat resistance of the copolymer of styrene and phenyl methacrylate is not high enough. As a result, if this copolymer is added to a highly heat-resistant PC resin with the objective of improving the melt fluidity, then there is a possibility that the heat resistance of the highly heat-resistant PC resin may decrease significantly.
Patent Document 2 proposes, as a method of improving the melt fluidity of a highly heat-resistant PC resin without reducing the heat resistance of the PC resin, a method in which a copolymer of styrene, α-methylstyrene and phenyl methacrylate is used as a fluidity improver and added to the PC resin. This method improves the melt fluidity of the highly heat-resistant PC resin, and causes no reduction in the heat resistance. However, because α-methylstyrene exhibits poor polymerizability, residual monomer tends to be readily retained within the copolymer, and this can generate silver streaks during molding, resulting in external appearance defects within the molded product.    [Patent Document 1]    International Publication No. 2005/030819 pamphlet    [Patent Document 2]    Japanese Laid-Open Patent Application No. 2006-306958